Conventionally, an image display device, which uses an organic EL (Electro Luminescence) element emitting light when holes and electrons injected into a light-emitting layer is recombined, is proposed.
In this type of the image display device, a thin film transistor (hereinafter, called “TFT”) formed of, for example, amorphous silicon, polycrystalline silicon, or the like, and an organic light-emitting diode (hereinafter, called “OLED”) or the like which is one of organic EL elements configure respective pixels. There is also known an image display device employing an active matrix system in which the brightness of respective pixels is controlled by setting appropriate current values to the respective pixels (refer to, for example, Japanese Patent Application Laid-open No. 2005-099715). Note that a threshold voltage at which a current starts to flow through TFT is different in each TFT.
Incidentally, in order to correct variations of threshold voltages Vth of TFTs employing the active matrix system, the threshold voltages Vth are detected by causing a gate and a drain of a target TFT to be conductive to each other to gradually discharge electrical charge accumulated in the gate of the TFT and to cause a gate potential to converge to the threshold voltage Vth.
However, to detect the threshold voltages Vth, it is necessary to first apply initial potential (Vth detection start potential) so that a gate-drain potential of the target TFT becomes greater than the threshold voltage Vth. If this initial potential is lower than the threshold voltage Vth, the threshold voltage Vth cannot be properly detected and an operation error is caused thereby.